Medical/surgical procedures requiring the step of tunneling subcutaneously between two locations for administration of a fluid to a patient are well known in the art.
Illustrative of such procedures is the relatively recent advancement in relieving intractable pain, e.g. in terminal cancer patients, by long-term epidural catheterization. In such procedures, an epidural catheter for administering a narcotic such as morphine extends subcutaneously from the paravertebral entry site where the catheter is introduced into the epidural space to an exit site on the flank where it is attached to a syringe or other source of narcotic to be introduced into the epidural space for pain management.
The tunneling step may be performed from the exit site for connecting the external portion of the catheter to the drug source toward the paravertebral entry site of the epidural catheter or, alternatively, it may be performed from the entry site to the desired exit site.
In either case, the tunneling device should not only be of sufficient length to provide a subcutaneous passageway between the two points in a single pass, but it must also be malleable so as to be capable to being shaped to conform to the shape of the body between these two points before tunneling is commenced.
To illustrate the state of the art pertaining to long-term epidural catheters, mention may be made of the Du Pen(TM) Long-Term Epidural Catheter commercially available from Davol, Inc., a subsidiary of C. R. Bard, Inc.
The Du Pen catheter system consists of three component parts: (1) an epidural catheter segment placed through a needle into the epidural space; (2) an exteriorized line equipped with an external luer connection and a subcutaneous Dacron cuff; and (3) a small splice segment to join the two catheter segments.
In view of the luer connection and cuff, it will be readily understood that the tunneling step must be from the exit site on the flank, e.g. from a subcostal location on the mid-nipple line toward the paravertebral incision provided for introducing the epidural catheter segment.
To accomplish subcutaneous tunneling procedures of the foregoing brief description, essentially two types of tunneling devices have heretofore been employed: (1) a solid tunneler of metal or plastic in which one end of the catheter to be tunneled is slipped over the trailing end of the tunneler (the end opposed from the leading end having the cutting tip) and then dragged through the passageway created by the tunneler; or (2) a hollow tunneler open at the trailing end and having an opening in the cutting tip of sufficient diameter to permit passage of the catheter therethrough, in which case after the tunnel is made and with the tunneler still in place, the catheter may then be threaded through the opening in the tip and out the trailing end of the hollow tumbler.
While either type of these malleable tunnelers is quite satisfactory most of the time, each does nevertheless possess inherent properties which may adversely affect the tunneling step.
Since the solid tunneler functions by dragging the catheter behind it through the passageway created by tunneling, it follows that the catheter is dragged through the debris of host origin caused by the tunneler. This may, in turn, cause certain problems requiring the tunneling and, in some instances the insertion of the epidural catheter itself to be repeated. First, kinking of the catheter may be caused. Secondly, any undue or sudden resistance in the advancement of the catheter behind the tunneler may cause the catheter to slip off the trailing end of the tunneler. Finally, if the epidural catheter is the component to be tunneled (as will be the case in the preferred long-term epidural catheter system contemplated for use with the present invention and which will be discussed in more detail hereinafter), any such resistance may cause the distal end of the epidural catheter to become dislodged from its position within the epidural space. Such dislodgement may or may not require the catheter to be removed and re-introduced into the epidural space, depending upon the extent of the dislodgement.
The second type of tunneling device heretofore used, namely the hollow tunneler having an opening in the cutting tip, does not suffer from the inherent dangers noted above. However, it may instead cause different problems.
Since the cutting tip at the leading end of the tunneler has an opening permitting passage of the catheter therethrough, there is a tendency for flesh, blood and/or other debris from the tunneling to enter the hollow tunneler through this opening at the leading end. This in turn may at least partially clog up the passageway within the tunneler, notably at the leading end, thereby impairing threading the catheter therethrough and possibly causing kinking within the tunneler. Additionally, some of this debris of host origin may enter the leading end of the catheter, thus providing an environment for infection due to bacterial contamination.
Stated simply, the task of the present invention is to provide a subcutaneous tunneling device which obviates the aforementioned inherent dangers when employing the tunnelers of the prior art, thereby providing a consistently efficacious device for accomplishing subcutaneous tunneling between two sites for the pain management or other medical procedure contemplated.